1. Technical Field
The present invention relates to transportation of a micrometer-sized object and extraction of mechanical work by a constant electric field.
2. Description of the Related Art
Conventionally, an alternating current electric field is used for oscillatory and periodic motion. In this case, motion occurs as a result of generation of a current.
In micrometer-sizes, since the Reynolds number representing a ratio of magnitude between inertial force and viscous force of a flow is low, it is considered to be difficult to extract work from mechanical motion.
Masahiko Hase, Shun N. Watanabe, and Kenichi Yoshikawa, PHYSICAL REVIEW E 74, 046301 2006 describes the effect of a constant electric field on a water droplet having a diameter of several tens μm in oil.
The micrometer-sized world which is a subject of the present invention is generally called the world of low Reynolds number. In the world of such a scale, it is known that work is not extracted only by making periodic motion on the straight line not having directionality. Therefore, it is impossible to extract work only by linear reciprocal motion as described in Non-Patent Document 1.
In light of this, it has been demanded to provide a technique capable of making an object move autonomously at will even in a constant electric field, transporting the same, and extracting mechanical work in micrometer-sizes.
Also, T. Mochizuki, Y. Mori, and N. Kaji, AIChE Journal 36, 1039 (1990); J. Eow, M. Ghadiri, and A. Sharif, Colloids Surf. A 225,193 (2003); Y. Jung, H. Oh, and I. Kang, J. Colloid Interface Sci. 322, 617 (2008); and W. D. Ristenpart, J. C. Bird, A. Belmonte, F. Dollar, and H. A. Stone, Nature 461, 377 (2009) are known. While these documents describe making a micro-object linearly move, they fail to make two-dimensional motion that is the most important for extracting work and lack any description of such idea.
In nanometer to micrometer scales, the Reynolds numbers are very low, and inertial force of an object does not play an important role, and motion of the object is rapidly attenuated by viscous force of the environment. Therefore, some driving energy should be supplied for continuously propelling the object. As described above, motion of a micro-object proposes a critical issue in a nonlinear system and a non-equilibrium system. In addition, the capability of propelling and controlling micro-objects such as biological polymers and cells is important in researches of applied physics and biological physics, as well as in MEMS and μTAS techniques, and plenty of appropriate techniques have been actively developed, however, they are far from practical use.